剪切增稠型电解质冲击载荷下的原位表征及力学-电化学耦合研究

Thermal runaway is an important factor affecting the safety of lithium ion batteries, which usually results from mechanical abuse. Improving the safety of electrolyte is very important to prevent thermal runaway in lithium ion batteries subjected to mechanical abuse. Thus, shear thickening electrolytes has been proposed to serve as the role of solid separator when batteries subjected to mechanical abuse, which could be one of effective solution to reduce the probability of short circuit and improve the safety of lithium ion battery. However, it is lack of the study of electrochemical performances for such electrolytes under impact loading and in-situ characterization of mechanical behaviors when fabricated batteries undergoing charging/discharging.In this project, a high-performance shear thickening electrolyte with stable electrochemical properties was designed to improve the safety of lithium ion batteries undergoing mechanical abuse. An in-situ method based on digital image correlation was developed to quantitatively measure and observe the mechanical behavior of shear thickening electrolyte under impact loading. We target to uncover the coupling mechanism between the real-time deformation of the shear-thickening electrolyte and the electrochemical response of assembled batteries under charging and discharging state. These can provide a useful tool and insightful guidance for optimizing the safety and performances of shear thickening electrolytes and next-generation lithium ion batteries.

热失控是影响锂离子电池安全性发展的关键因素，而机械滥用是引发锂离子电池热失控是最重要的原因之一，提高机械滥用下电解质的安全性对于防止电池热失控至关重要。而剪切增稠型电解质在受到冲击载荷后转变为类固体所表现出的阻隔作用，能有效降低锂离子电池短路导致热失控的风险，但是目前尚缺乏对剪切增稠型电解质在冲击载荷下电化学性能的研究，其在充放电状态下的原位变形观测还尚未开展。本项目从提高在机械滥用下的电池安全性角度出发，通过设计电化学性能稳定的剪切增稠型电解质，并发展一种基于数字图像相关的剪切增稠型电解质原位表征方法，对其在冲击载荷下表现的类固体力学行为进行定量测量和观测，研究电池充放电状态下剪切增稠型电解质实时变形演化与电池电化学响应之间的耦合关系，为高性能剪切增稠型电解质的设计优化以及锂离子电池的安全评价提供实验工具和分析指导。

锂离子电池的安全性是制约其在电动汽车等领域深度应用的关键性因素。机械滥用则是引发锂离子电池热失控等安全性问题最重要的原因之一。因此，提高电池在机械滥用下的结构、性能稳定性对改善电池的安全性至关重要。基于此，本项目以提高机械滥用下的电池安全性为目标，制备了系列具有高离子电导率的剪切增稠型电解质，研究了剪切增稠型电解质的性能调控规律和作用机制，实现了对锂离子电池的良好冲击防护效果和锂枝晶均匀生长促进作用，有效提高了电池的稳定性和安全性。同时，基于数字图像相关法，搭建了载荷作用下锂离子电池力-电化学耦合原位测试装置，原位观测并表征了工作状态下含剪切增稠型电解质的软包电池受冲击载荷时的表面应变演化和电化学响应行为，解析了含剪切增稠型电解质电池的力学-电化学性能耦合关系，为高安全锂离子电池的设计和评估提供了数据支撑和参考。